The Effect of Rice Husk on the Chemical Properties of Clay Soil Hamzat Isah Abstract---This paper tends to evaluate the variations in compressive strength developed between ordinary and improved compressed earth brick earth stabilized with rice husk ash (RHA) at different percentage of RHA additions ranging from 0.0%, 2.5%, 5.0%, 7.5%, 10.0% and 12.5% by weight of dry soil at various curing periods of 14, 21 and 28days respectively. The Clay soil sample collected from Bambami village of Batagarawa Local government of Katsina state Nigeria, while the Rice Husk were obtained from Dandume local government of the same state. the results revealed that, a compressed earth brick (CEB) when stabilized with a rice husk ash is comparable with other bricks in every respect and can perform well in modern construction work and demonstrates the properties and shows its good effect when compared with conventional bricks especially in terms of strength and durability at 10.50% and 12.50% curing period of 28days with compressive strength of 3.98N/mm 2 , 3.80N/mm 2 respectively, while the ordinary un-stabilized compressed bricks with 0.00%(control group) recorded with 1.00N/mm 2 as the highest compressive strength value obtained at curing period of 21dyas among the other control samples. However, other parameters measured indicate that, increase in optimum moisture content (OMC) and decrease in maximum dry density (MDD) with increase in percentage addition of RHA. There was also improvement in CBR and Ultimate bearing capacity with increase in addition of RHA content. The result also indicates that maximum dosage of RHA is between 10% and 12.5%. The study therefore, concluded that rice husk ash can be used as an alternative soil stabilization agent for improving the properties of soft clay soil in making compressive earth brick suitable for load bearing walls of not more than two stories in areas where the rice husk is available. Keywords--- Rice Husk ash, Compressive Strength, Brick Earth, Stabilization, I. INTRODUCTION Building with earth is one of those ancient technologies which still remain alive in the place untouched by industrialization. Innovation, however, has evolved low strength sun dried adobe into burnt clay brick with more strength gained. Mounted interest in searching sustainable green building material has created compressed earth stabilized brick which attract people for its low carbon emission especially in the production stage. (Riza, Fetra Venny 2011) Hamzat Isah, Department of Building Technology College of Environmental Studies, Hassan Usman Katsina Polytechnic, email id: hamzat4u@gmail.com /+2348030660213 Rice husk ash (RHA) is a pozzolanic material that could be potentially used in soil stabilization, though it is moderately produced and readily available. When rice husk is burnt under controlled temperature, ash is produced and about 17%-25% of rice husk’s weight remains ash. (Mohammed Y. Fattah 2013) The combustion of agricultural residues volatizes the organic matters and a silica-rich ash is produced. Of all the agricultural wastes, rice husk yields the largest quantity of ash with about 93 per cent silica which gives it puzzolanic properties. When burned in ordinary way rice husks produce a crystalline silica ash. However, if burned under suitable conditions, a highly reactive black non-crystalline silica residue having puzzolanic properties is produced. Temperature and duration of combustion are of utmost importance for good quality rice husk ash. The right temperature is 700°C for 2-3 hours. Thus, a controlled combustion of rice husk in electricity generation plants produces amorphous or non-crystalline silica with about 85-90 per cent cellular particles. These particles are highly micro porous and possess a very high specific surface (5 × 105 to 10 × 105 cm2/g). Rice husk ash when mixed with soil (20 %), instead of lime sludge, produces excellent binding properties. This binder when used as 30 per cent in mixture with Portland cement gives the properties of Portland puzzolana cement (Duggal, 2008). II. INVESTIGATIONS The impact of rice husk ash (RHA) has been investigated on a soft clay soil on the natural moisture content, compaction test, C.B.R, Shear and compressive strength tests at various percentages of RHA additives. III. MATERIALS AND PROCEDURE Clay soils used were obtained from Bambami village of Batagarawa local government of Katsina, Nigeria. The soil was taken to the geology and soil mechanic laboratory of civil engineering Department Hassan Usman Katsina Polytechnic, where by the Natural moisture content, Specific gravity, Atterberg limit, Compaction test, Sieve analysis, C.B.R, Shear box and compressive tests was performed on the clay using various percentage of RHA and using 0% of addition as a control. A compaction and C.B.R test was conducted on the mixed soil using heavy compaction in accordance with the procedure of BS 1377: Part 4: 1990. Also Atterberg limit test, Specific gravity, Shear box and compressive strength tests was performed at various percentage of the RHA addition of the soil bulk density in accordance with the procedure of BS 2nd International Conference on Chemical, Biological, and Environmental Sciences (ICCBES’15) May 20-21, 2015 Dubai (UAE) http://dx.doi.org/10.17758/IAAST.A0515036 9